A conventional color cathode ray tube is disclosed in, for example Japanese Patent Laid Open Gazette No. 55-76553, in which an electron beam reflecting film comprising bismuth oxide (Bi.sub.2 O.sub.3) as a main element and binder such as water glass is mixed therein is formed on an electron beam irradiated surface of a shadow mask.
According to the above shadow mask, when an electron beam with high energy is irradiated on the surface of the shadow mask, doming, caused by an increase of a temperature of the shadow mask, can be prevented by increasing the ratio of the number of electrons elastically or inelastically scattered backward to the number of irradiated electrons, that is, the backward scattering coefficient. Thus, almost 30% of the irradiated electron beam energy is scattered backward.
In addition, such doming preventing technique is reported in detail in Japan Society of Electronics, Information, and Communication Engineers, "Doming prevention of CRT shadow mask by electron beam reflecting film", published on Feb. 9, 1989.
According to the conventional color cathode ray tube, an anti-doming effect obtained by the electron reflecting film formed on the shadow mask is approximately 30%, which is not sufficient for a large sized color cathode ray tube.
In addition, it has been conventionally proposed that a film comprising metal tungsten as a main element is formed on a surface of the shadow mask instead of the film comprising Bi.sub.2 O.sub.3 as a main element. When the film comprising metal tungsten as a main element is used, the anti-doming effect can be 50% in theory. As a result of ardent study by the inventors of the present invention over a long period of time it has been found that performance of the film can be improved by 50% or more, as compared with that of the film comprising Bi.sub.2 O.sub.3 as a main element.
However, in case of the film comprising metal tungsten as a main element, since manufacturing process in which the film is baked is usually used, oxidation occurs the tungsten powder. As a result, the substantial anti-doming effect by the tungsten film is approximately 35%, which is almost the same as that of the conventional film comprising Bi.sub.2 O.sub.3 as a main element.